- introduce tile exchange for HEFFITD, AREAITD, and HSNOWITD; - move calls to DIAGNOSTICS_FILL for SIheffN and SIareaN   from seaice_model.F to seaice_diagnostics_state.F
- introduce tile exchange for HEFFITD, AREAITD, and HSNOWITD;
- move calls to DIAGNOSTICS_FILL for SIheffN and SIareaN
  from seaice_model.F to seaice_diagnostics_state.F

altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h